1. Field of the Invention
The present invention relates to an electric power generation control apparatus for a vehicle alternator, capable of controlling an output voltage of the vehicle alternator by adjusting an exciting current of the vehicle alternator, in particular, relates to an electric power generation control apparatus capable of preventing hunting of a rotation speed of the vehicle alternator.
2. Description of the Related Art
An idling rotation speed of an internal combustion engine mounted on a motor vehicle is more decreased in order to meet a recent requirement of low fuel efficiency. On the other hand, a vehicle alternator more and more generates and outputs a high electric power in order to meet a recent demand. As a result, the electric power generation of the vehicle alternator greatly affects the rotation speed of the vehicle alternator during engine idle.
For example, Japanese patent laid open publication No. JP S62-064299 (corresponding family U.S. Pat. No. 4,636,706) has disclosed a technique capable of suppressing a rapid increase of an electric power torque of a vehicle alternator by gradually increasing an exciting current of the vehicle alternator in order to prevent decreasing the rotation speed of an internal combustion engine in the motor vehicle caused by such a rapid increase of the electric power torque of the vehicle alternator when an electrical load is entered or connected during engine idle.
Japanese patent laid open publication No. JP 2003-284257 (corresponding family U.S. Pat. No. 6,900,618) has disclosed a technique capable of setting a limit value of an exciting current of a vehicle alternator and of controlling an exciting current flowing in an exciting coil of the vehicle alternator so that the exciting current does not exceeds the limit value in order to prevent the occurrence of unstable rotation speed of an internal combustion engine caused by increasing an electric power torque of the vehicle alternator in fluctuation of the electrical loads and rotation speed of the internal combustion engine.
Further, Japanese patent No. 3,509,007, one of inventors thereof is the same inventor according to the present application) has disclosed a technique capable of increasing/decreasing an adjustment voltage according to increasing/decreasing the rotation speed of an internal combustion engine in order to suppress a hunting phenomenon during engine idle where rotation speed of the engine is continuously vibrated by fluctuation of an electric power generation torque.
However, it is impossible to adequately suppress the hunting phenomenon described above during engine idle only by relaxing the fchange of the exciting current disclosed in Japanese patent laid open publication No. JP S62-064299.
Further, although the technique disclosed by Japanese patent laid open publication No. JP 2003-284257 suppresses the hunting phenomenon, a voltage fluctuation occurs in a storage battery by discharging the electric power of the storage battery by decreasing the electric power generation amount of the vehicle alternator. As a result, such a voltage variation of the storage battery causes a problem of flicker of a head lamp of a motor vehicle.
Still further, the technique disclosed by Japanese patent No. 3,509,007 capable of controlling the adjustment voltage causes changing the rotation speed of the vehicle alternator by an impertinent adjustment timing. Thus, this technique involves a difficulty of adjustment such timing.